Exam 3: Endocrine and Reproductive Systems Flashcards
What is the endocrine system responsible for?
communication and coordination (along with NS)
uses chemical signals called hormones
includes multiple organs spread throughout the body
Nervous system vs. endocrine system
both participate in communication
but differ in their speed and means or signaling
Nervous system:
uses both electrical and chemical signaling, electrical: direct action of electrical potential, chemical: neurotransmitters, very rapid response (milliseconds)
Endocrine system”
uses chemical signaling only, chemical: hormones transported in blood stream, slower response (seconds to days), less specific (may have different effects in different cells)
Both systems are connected: fight or flight response
What are the major organs of the endocrine system?
pituitary gland, adrenal gland, thyroid gland, parathyroid gland, pancreas, pineal gland, thymus, gonads
What are the secondary organs of the endocrine system?
skin, heart, GI tract, kidneys, liver, placenta, adipose tissue
exocrine vs. endocrine glands:
Exocrine: release secretions through ducts, ex: sebaceous and sweat glands of skin, liver (bile), pancreas (digestive juices)
Endocrine: ductless, secrete hormones into surrounding fluid
dense capillary networks or lymphatics pick up hormones and transport them
What are the other local chemical messengers?
Hormones: diffuse into blood or lymph and travel throughout the body
Autocrines: chemicals that elicits response in the same cell that secreted it
Paracrines: induces a response in neighboring cells
What are the two major groups hormones can be divided into?
hormones derived from amino acids
includes amines, peptides, and proteins
hormones derived from lipids
includes steroids
affects hormone distribution and type of receptor is binds to
Explain amine hormones:
synthesized form amino acids tryptophan or tyrosine (amino acid structure modified)
Explain peptide and protein hormones:
differ in amino acid chain
peptide: short chain
amino acid: long chain
synethsized like other body proteins DNA->mRNA->amino acid chain
Peptide: ADH
Protein: growth hormone
Explain steroid hormones:
derived from lipid cholesterol
not soluble in water
must travel bound to transport protein, extends half life of the hormone
ex. testosterone and estrogen
Explain the action of hormones:
hormones bind to a hormone receptor -> protein located inside the cell or within the cell membrane, receptors are specific (recognize hormones with specific shapes and side groups)
Binding of hormone to receptor initates a response
same type of receptor in different tissue may trigger different response (ex. epinephrine)
what are the responses of hormones?
stimulation of protein synthesis
activation/deactivation of enzymes
changes to cell membrane permeability
altered rates of mitosis and cell growth
stimulation of product secretion
What is an intracellular hormone receptor?
receptors located inside the cell
hormones must be able to cross cell membrane
steroid hormones can diffuse through bilayer, thyroid hormones have carrier proteins
binding to receptor creates hormone-receptor complex -> binds to DNA -> triggers transcription of target gene to mRNA, followed by protein synthesis
What is a cell membrane hormone receptor?
receptors located on cell surface
amino acid derived hormones cannot diffuse through bilayer (exception: thyroid hormones)
binding to receptor initates signaling cascade, carried out by secondary messenger, usually cAMP
What is a phosphorylation case in cell membrane hormone receptors?
phosphorylation of proteins can trigger a variety of effects:
changes to nutrient metabolism
synthesis of different hormones and other products
increases efficiency, speed, and specificity or hormonal response
1000s of signaling events can be triggers simultaneously, can respond to low concentrations of hormone in blood stream
signal duration is short -> cAMP is deactivated by enzyme PDE
What is a target cell?
for a target cells to respond to a hormone, it must have specific receptors that the hormone can bind to
target cell activation depends on: blood levels of the hormone, number of receptors for that hormone on or in target cell, affinity if binding between hormone and receptor
What is a large vs reduced hormonal effect?
large: higher hormone levels, more receptors, higher affinity
reduced: lower hormone levels, fewer receptors, lower affinity
How are hormone receptors regulated? up and down
up regulation: low levels of hormone increases the number of receptors for that hormone, cells become more sensitive to hormone
downregulation: high levels of hormone causes decrease in the number of receptors for that hormone, cells become less reactive to excessive hormone levels
how can hormones interact?
two or more hormones can interact to affect response of cells
permissive effect: presence of one hormone allows a another to act
synergistic effect: two hormones with similar effects produce amplified response, two hormones may be required for the cells to respond at all
antagonistic effect: two hormones have opposing effects
what system regulates hormones?
negative feedback systems, some are positive
Manufacture and release of hormones can be triggered by:
humoral stimuli: changing blood levels of ions and nutrients triggers hormone secretion
neural stimuli: nerve fibers stimulate hormone release
hormonal stimuli: endocrine glands release hormones in response to hormones produced by other glands
negative feedback vs. positive feedback:
negative: response is reverse of change detected
postive: response reinforces change detected
what are the secondary endocrine organs?
heart
GI tract
kidneys
skeleton
adipose tissue
thymus
liver
What is sexual reproduction?
combine genes from two parents
union of two gametes to form zygote (fertilized egg), male gametes: sperm, female gametes = egg
sexes typically defined by their sex chromosomes (male XY and female XX)
What are the primary and secondary sex organs in males?
primary: produce gametes-> testes
secondary: necessary for reproduction -> penis, ducts, glands
What is spermatogenesis?
sequence of events that produce male gametes (sperm). starts at puberty, continues daily, ~120 million sperm made daily
What is the site of spermatogenesis?
testes, sperm production occurs in the seminiferous tubules: surrounded by interstitial endocrine cells (leydig cels) -> secrete testosterone into interstitial fluid
What are spermatogenia?
immature germ cells, 2-3 layers on inner surface of semiserious tubules, form from primordial germ cells that migrate into testes during embryonic development
do spermatogenia undergo mitosis?
yes!
type A daughter cells remain to maintain germ line
type B daughter cells migrate towards lumen and are surrounded by nurse cells (Sertoli cells) -> become spermatocytes
What are nurse cells?
aka supporting cells, Sertoli cells
blood-testis barrier: connected by tight junctions of nurse cells, prevents immune system from attacking sperm antigens
support sperm: regulate nutrients, hormones, environmental toxins that can enter tubules, waste removal
Primary and secondary spermatocytes:
primary: undergo meiosis I -> produced 2 haploid cells called secondary spermatocytes -> undergo meiosis II -> produces 4 spermatids with 23 chromosomes in each
What is a spermatid?
not quite sperm cells, small ,round, large nucleus, non-motile
What is spermiogenesis?
spermatids elongate, shed cytoplasm, form tail
now a sperm!
head with flattened nucleus -> genetic storage, acrosome
tail (flagellum) -> locomotor apparatus, mid piece (mitochondria = ATP)
How are sperm stored?
sperm are stored in epididymis and vas deferent (may remain for month, kept inhibited)
How do sperm move?
using flagella
1-4mm/min, movement enhances in neutral-slightly alkaline conditions (semen), increase in temperature will decrease activity, live 1-2 days after ejaculation
Explain abnormal spermatogenesis:
What do the darts and cremaster muscles do?
increase in temperature will decrease spermatogenesis
scrotum maintains testes at lower than body temp
necessary for sperm production
Dartos: smooth muscle that wrinkles skin-> pulls closer to body
Cremaster: skeletal muscles that elevates testes -> pulls closer to body
What does the pampiniform plexus do?
absorbs arterial heat
countercurrent heat exchanger -> blood entering the testes is cooled by blood leaving the testes
What hormones are present in the male reproductive system?
GnRH, FSH, LH and testosterone
What is the HPG axis?
FSH stimulates cells to release androgen-binding protein which keeps high [testosterone] near spermatogenic cells
inhibition: testosterone feeds back to hypothalamus to inhibit GnRh, when sperm count is high, inhibit is released -> inhibits release of GnRH and FSH
What is testosterone?
secreted by Leydig cells in testes
~20% of the mass of testes, increase in number after puberty
What does testosterone do before brith, during puberty and as an adult?
Before brith: masculinizes reproductive tract and external genitalia
Puberty: spermatogenesis, initials growth and development of male reproductive organs, secondary sex characteristics, sex drive, bond growth
Adult: maintain functions initiated in puberty
What are the two phases of the male sexual response?
erection and ejaculation